The Barrel pizza oven is also known as the vault. It is made of brink and takes the shape of half a barrel. The inner side of the vault is rectangular. This type of oven is common is commercial facilities even though it is still used in homes. It is commonly used for baking bread. Because of its rectangular shape, it is not very effective in cooking pizza due to none even heat concentration in the oven. To create the curved dome required a supporting frame. Here is the process of How to construct a pizza oven dome out of brick.
Further information: Types of wood fired pizza ovens